Comparative study of the mechanical behaviour of Castaman external fixator in different mounting configurations

The mechanical behaviour of the Castaman external fixator was determined using different mounting configurations in a system that simulated a long bone fracture during the formation of the bone callus. The first stage of the study was the determination of the stress-strain characteristics of the system with monolateral mounting. The second stage, the object of this study, is the analysis of the system with bilateral mounting and a comparison between the two configurations of the external fixator examined. Strain gauge analysis was used to determine the strains and stresses in the various elements of the system (fiches and external unit). Numerical techniques (FEM) were also used in order to confirm the results obtained using the simulation system. The results obtained show clearly the greater stiffness of the bilateral system. Combined bending and compressive stresses are present on both the screws and the external units, and reveal a little asymmetrical behaviour due to the conicity of the screws.